The present application relates generally to communications between computer devices and, more particularly, to multiplayer peer-to-peer connections across firewalls and network address translators (NATs), using a single port number on each computer device.
More and more applications attempt to create a peer-to-peer connection between two hosts to transfer data. However, it is non-trivial to achieve such a connection in case one or both of the hosts are behind a firewall, especially if it also does network address translation, as is the case with the great majority of business and home firewalls nowadays. For home use, people often use a device that is a combination of a router, firewall and NAT. The problem is even further complicated in the case where a host attempts multiple peer-to-peer connections at the same time through a single port. This is exactly the way in which many PC and console games doing peer-to-peer data exchange work.
An additional challenge is to be able to set up a new connection through a single (private) port of the host, all the while transferring data through that same port with other hosts. This is a situation commonly found in network games where people meet in a lobby, and where as soon as a new user joins, he or she can start talking to the other users through voice chat using a headset.
Currently most peer-to-peer applications only have basic support for firewall/NAT traversal. The result is that if a host happens to be behind a difficult to traverse firewall/NAT, the host's online experience will be poor because a lot of connections will fail.
One solution game publishers have used is to instruct gamers to do port forwarding on their firewalls/NATs. However, this is a complicated operation for the average user and potentially creates a security hole in the firewall. Furthermore, this solution fails when two users are behind the same firewall.
Another solution adopted by Microsoft® in the XBox™ gaming console is to display on the support site a list of compatible and incompatible router devices. Indeed, some firewalls are more difficult to traverse than others, and in the case of Microsoft® the technology will enable peer-to-peer connectivity between hosts behind “easy” firewalls/NATs, but not behind more difficult ones. But often users already have a firewall before they buy a game. In case they use a firewall that is not supported by the game, they will run into problems to play online.